Project Summary: The mechanisms by which eukaryotic cells control the synthesis of membrane lipids in coordination with ongoing membrane biogenesis are not well understood. Yet phospholipids, particularly inositol-containing phospholipids, have been implicated in complex signaling processes which play a role in controlling cell growth and proliferation in higher eukaryotes. Yeast cells synthesize a typically eukaryotic mixture of phospholipids, using pathways which are similar to those in higher eukaryotes. This organism can be manipulated using powerful molecular genetics and analyzed using new genome-wide techniques. The proposed analysis will produce a detailed model of the relative inputs and interactions of multiple signaling pathways influencing phospholipid metabolism, an essential cellular process which itself produces signals that feedback to produce autoregulatory loops and influence other metabolism, membrane trafficking and signal transduction pathways. A genetic assessment will be conducted of the combinatorial inputs and interactions of cellular processes influencing, and influenced by, phospholipid metabolism in yeast including, membrane trafficking, silencing and signaling. Methods which allow quantitative determination of 100 or more metabolites in a single experiment will be used to assess lipid metabolism in selected mutants and their suppressors in order to identify metabolic signals influencing this regulation. Microarray analysis will be used to explore the kinetics of gene expression, genome wide, in response to changes in lipid metabolism. Relevance: An understanding of the regulation of lipid metabolism is critical in dealing with chronic conditions such as obesity, diabetes, and atherosclerosis. Yeast is an excellent model system for such studies since the relevant pathways are common to yeast and mammals and the major enzymes are homologous, ensuring that insights derived from yeast will generate knowledge relevant to human health.